Applicant is aware of U.S. Pat. Nos. 4,275,546; 4,286,424; 4,306,403; 4,496,105; 4,720,963; 4,776,154; 5,558,163; 5,592,029; 5,819;512 and. 5,921,071, the disclosures of which are incorporated by reference herein.
In machines of conventional design, the cutting cylinder typically has a switchable drive element connected thereto, and a drive train, for driving the rollers of an intake subassembly equipped with a foreign body detecting device. A reversing transmission unit for driving the intake subassembly in the reverse direction, and a cut-out clutch for bringing the intake subassembly to a sudden halt are mounted in the drive train. The cut-out clutch is moveable into one position for transferring the driving torque and into another position for blocking the rotation of the intake subassembly.
In conventional forage harvesters, the cutting cylinder is usually driven directly by the main drive system. The switchable drive element connected to the cutting cylinder may be a belt drive arrangement with a driving pulley fixed to the shaft of the cutting cylinder. The driven pulley is mounted on a shaft having a clutch at the opposite end thereof and this clutch is coupled to another clutch via toothed gears. The two clutches form part of the switchable transmission system and provides the forward and reverse rotation of the intake mechanisms of the forage harvester. The clutch on the cutting cylinder shaft also meshes with a gear wheel forming the input of a transmission unit. The cut-out clutch is also coupled to this transmission unit so that the rollers of the intake subassembly can be brought to a sudden stop should this be necessary. This transmission unit transfers the torque via further gears of the switchable transmission system to a shaft which applies the torque to a spur gear in order to drive the feed rollers and the compression rollers. A drive system of this type has the great advantage that, in the case where a rapid stop is needed due to the presence of a foreign body or an overload of the intake mechanism, the cutting cylinder of relatively large mass can continue to rotate, but the feed rollers and the compression rollers can be brought to a sudden stop. The masses subjected to braking are thereby kept as low as possible. In order to remove the foreign body or to disperse the overload on the intake mechanism, the rollers of the intake subassembly are driveable in the reverse direction.
The selection of the rotational direction of the intake subassembly may be controlled by the driver of the forage harvester by actuating switching elements in the driver's cab. If the intake subassembly is suddenly halted, the belt tensioner for the belt drive arrangement connected to the cutting cylinder is simultaneously moved by means of a hydraulic cylinder to relieve the tension on the belt. The whole intake subassembly is decoupled from the rotating cutting cylinder and comes to a sudden stop. Typically the feed rollers have to be reversed, to clear a foreign body, for example, and to deactivate the rapid-stopping device. For this purpose, a switching element may be actuated by the driver for switching over the reversing transmission unit and connecting up the belt drive arrangement. In general, a foreign body or an overload of the intake mechanism that caused the rapid-stoppage is fed out of the intake zone by the reversing process.
A method of disabling a spur-gear type reversing transmission unit is known from DE 30 29 050. The design of the drive system is such that a motor driven belt drive arrangement is used, inter alia, to drive a spur-gear type reversing transmission unit via a further belt drive arrangement, two electromagnetically operable clutches being arranged on the output shaft of this transmission unit. A spur gear connected to one clutch meshes with a spur gear on the input shaft and a spur gear associated with the second clutch likewise meshes with a spur gear mounted on the input shaft but via an intermediary gear. The purpose of this arrangement is to bring the rotating components to a complete halt in as short a time as possible. For this purpose, the two electromagnetically operable clutches are actuated simultaneously and the intake mechanism is blocked.
This prior drive arrangement is suitable for halting the rollers of the intake subassembly and the cutting cylinder in the event of an overload of the intake subassembly, as are conventional arrangements generally. In this case, there is substantially much more time available than is the case where the foreign body detecting device responds, if the device is to prevent the foreign body from entering the area swept by the cutting cylinder. If the two clutches of the prior device are actuated simultaneously, there is still a relatively large amount of run-on time available. The time needed to stop the rollers, upon the detection of a foreign body, may be too great to reliably prevent a foreign body from entering the area swept by the cutting cylinder.